Our initial studies of afferent synaptic release sites in chick cochlear hair cells focused on a relationship between whole cell electrophysiological recordings of calcium current and the number of presynaptic dense bodies (thought to be involved in transmitter release) observed at the terminal site in random sections across the cochlea. Although we could establish a fairly close correlation between increased calcium current and an increased number of presynaptic dense bodies, we did not have a good 3-D picture of what was going on in the whole cell (i.e., the total number of dense bodies per cell, the structure of the dense body, association with membrane and cell components, etc.). The HVEM has proven to be an effective tool for reconstructing sectioned hair cells, especially when combined with the available computer equipment and programs at the Boulder facility. HVEM has provided us with actual numbers of dense bodies per cell rather than just numbers per thin section. Additionally, our reconstructions have provided us with a better understanding of the structure of presynaptic dense bodies (which differs in tonotopically distinct regions of the cochlea), as well as their association with transmitter vesicles and the plasma membrane. To date, we have reconstructed thirty-six cells from three distinct regions of the chicken cochlea.